Clever! I'm really enjoying your tech/architectural filters; they're very realistic and have a nice set of controls for tweakage fun.
Of course, lovely realistic texture filters come at a price -- rendering time. Luckily, there are often shortcuts and work-arounds that you get to learn after playing with FF for a long time. I'm afraid I got nosey and poked around in Slider Control Panel to see what might be done in this line. I came up with a version that looks very similar (not exact) to your original, but which renders
much more quickly.
If you're interested, I can send you the .ffxml by e-mail so you can poke around in it. Forgive me if I'm being too presumptious.
Here's an example:

Kat
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"Listen, gotta dash, things happening. Well, four things. Well, four things and a lizard." -The Doctor